Mixing valve

ABSTRACT

A mixing valve ( 10 ) includes a valve body ( 12 ) having a hot fluid inlet ( 14 ), a cold fluid inlet ( 16 ), a mixed fluid outlet ( 18 ), and a cavity ( 20 ) in the valve body ( 12 ) between the inlets ( 14, 16 ) and the outlet ( 18 ). Mixing valve ( 10 ) includes a liner ( 30, 130, 230, 430, 530, 630, 730, 830 ) positioned in valve body ( 12 ) and a valve member ( 40, 140, 240, 340, 440, 540, 640, 740, 840 ) movable therein between a first position restricting the flow of hot fluid and a second position. Liner ( 30, 130, 230, 430, 530, 630, 730, 830 ) includes a downstream valve seat ( 74, 174, 274, 474, 574, 674, 774 ) that, when engaged by valve member ( 40, 140, 240, 340, 440, 540, 640, 740, 840 ), restricts flow of hot fluid past valve member ( 40, 140, 240, 340, 440, 540, 640, 740, 840 ).

CROSS-REFERENCE TO RELATED APPLICATION

This application is a nationalization of and claims the benefit ofco-pending PCT Application Number PCT/US02/27056 having InternationalPublication Number WO 03/019315 A1 filed 23 Aug. 2002, which claims thebenefit of U.S. Application Ser. No. 60/314,803 filed 24 Aug. 2001.

FIELD OF THE INVENTION

This disclosure relates to mixing valves. More particularly, thisdisclosure relates to valves for mixing a first fluid with a secondfluid.

BACKGROUND AND SUMMARY

Mixing valves having valve bodies configured to combine flows of hot andcold fluids to provide a controlled mixed fluid temperature are known.Examples of such mixing valves using thermostatic control are shown inU.S. Pat. Nos. 6,315,210, 5,647,531, 5,379,936, 5,323,960, 5,203,496,and 5,011,074, the disclosures of which are hereby expresslyincorporated by reference herein, the applicant/inventor in the presentapplication being an inventor in each of these patents.

A mixing valve includes a valve body having a hot fluid inlet, a coldfluid inlet, and a mixed fluid outlet. The valve body includes a cavitybetween the inlets and the outlet. In one embodiment, a first seat and asecond seat are in the cavity, and a valve member in the cavity ismovable between a first position engaging the first seat and a secondposition engaging the second seat.

In one aspect of the disclosure, a liner in the cavity includes thefirst and second seats. In another aspect of the disclosure, the valvemember includes a weep opening to permit restricted flow of at least thehot fluid. In another aspect of the disclosure, the valve memberincludes a plurality of spaced apart mixing fins.

In another aspect of the disclosure the mixing valve includes a liner inthe cavity, the liner including a hot liner inlet and a cold linerinlet. In one implementation of this aspect, the second seat is betweenthe cold liner inlet and the first seat. In another implementation ofthis aspect, the cold liner inlet is between the first seat and thesecond seat. In another implementation of this aspect, the valve memberis a poppet-style valve member and the hot liner inlet is a bore in afloor of the liner.

Additional features will become apparent to those skilled in the artupon consideration of the following detailed description of illustrativeembodiments exemplifying the best mode of carrying out the drop leafsupport apparatus as presently perceived.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a sectional view taken through a valve body of athermostatic mixing valve to expose hot and cold fluid inlets and amixed fluid outlet in communication with a liner in the valve body shownin section to reveal a valve member movable in the liner to restrictflow from the hot and cold liner inlets in response to movement of athermostat assembly that senses the mixed fluid temperature;

FIG. 2 illustrates a fragmentary sectional view similar to FIG. 1showing the thermostat assembly in section to reveal a thermostat body,a bellows sealably coupled thereto, a thermally responsive fluid in thethermostat body, and an actuator coupled to the thermostat to cooperatewith the valve member to move the valve member in the liner;

FIGS. 3A-3D illustrate a sequence in which a valve member moves in aliner having a hot liner inlet, a second seat, and a cold liner inletbetween the second seat and the hot liner inlet, the valve member beingmovable between a first position engaging a first seat in the liner toclose the hot liner inlet and a second position engaging a second seatto restrict flow of fluid from the hot liner inlet;

FIG. 3A illustrates a cross sectional view taken through a center of theliner and valve member showing the valve member in the first positionengaging the first seat and spaced apart from the second seat;

FIG. 3B illustrates the liner and valve member of FIG. 3A spaced apartfrom the first and second seats, with sides of the valve member stillblocking flow through the hot liner inlet;

FIG. 3C illustrates the liner and valve member of FIG. 3A positionedbetween the first and second seats and oriented to permit flow of hotand cold fluids through the hot and cold liner inlets;

FIG. 3D illustrates the liner and valve member of FIG. 3A in the secondposition engaging the second seat, and a disc at a downstream end of thevalve member engaging the second seat, the disc formed to include a weepopening to permit restricted flow of the hot and cold fluidstherethrough when the valve member engages the second seat;

FIG. 4 is a sectional view taken through the center of an alternativeliner and valve member, the second seat positioned between the hot linerinlet and the cold liner inlet;

FIG. 5 is a top view of an alternative valve member having mixing finsextending radially outwardly from the valve member;

FIG. 6 is a sectional view taken generally along section line 6-6 ofFIG. 5, through the center of a valve member showing mixing finsextending from a disc at a downstream end of the valve member, themixing fins including a surface generally perpendicular to an axisthrough the liner;

FIG. 7 is a sectional view through the center of a valve member similarto that of FIG. 6, the mixing fins including a surface facing radiallyinwardly and in an upstream direction;

FIG. 8 is a front view of a valve member similar to that of FIG. 6, themixing fins including a surface that is slanted;

FIG. 9 is a sectional view through the center of an alternative linerand valve member, the cold liner inlet being between the second seat andthe hot liner inlet, and the valve member including a cold inlet slot,the cold liner inlet being closer to the hot liner inlet than the secondseat;

FIG. 10 is a sectional view through the center of an alternative linerand valve member, the hot liner inlet being a bore in the floor of theliner, the second seat being between the cold liner inlet and the bore,and the valve member being a poppet movable between a first positionengaging the first seat to close the bore and a second position engagingthe second seat, the valve member including a centering portion;

FIG. 11 illustrates a bottom view of the liner and valve member of FIG.10 showing the floor of the liner and the centering portion of the valvemember in the bore;

FIG. 12 illustrates a sectional view similar to FIG. 10 of analternative liner with the cold liner inlet being between the hot linerinlet and the second seat;

FIG. 13 illustrates a fragmentary sectional view of a portion of analternative liner and valve member, the hot liner inlet being a bore andthe valve member including a downstream portion engaging the bore toclose the hot liner inlet when the valve member is in a first position,and a disc outside the liner when the valve is in the first position andengaging the bore to close the hot liner inlet when the valve member isin a second position; and

FIG. 14 illustrates a sectional view through the center of analternative liner and valve member, the liner including a first seatadjacent a hot liner inlet formed as a bore, a cold liner inlet, and asecond seat between the hot and cold liner inlets, the valve memberbeing a poppet and including an upper piston to throttle the flow ofcold fluid, the poppet movable between a position engaging the firstseat and a position engaging the second seat.

DETAILED DESCRIPTION

Referring now particularly to FIGS. 1 and 2, a mixing valve 10 includesa valve body 12 having a hot fluid inlet 14 coupled to a source ofrelatively hot fluid and a cold fluid inlet 16 coupled to a source ofrelatively cold fluid. Valve body 12 also includes a mixed fluid outlet18 and a cavity 20 formed in valve body 12 between the mixed fluidoutlet 18 and the hot and cold fluid inlets 14, 16. A hot fluidpassageway 22 extends between hot fluid inlet 14 and a hot inlet port 24to cavity 20. Hot inlet port 24 is adjacent a first end 26 of cavity 20.A cold fluid passageway 32 extends between cold fluid inlet 16 and acold inlet port 34 to cavity 20. Cold inlet port 34 is positioneddownstream relative to hot inlet port 24. Cavity 20 includes a mixingregion or chamber 23 in which hot and cold fluids are mixed prior toexiting valve 10 through mixed fluid outlet 18.

As shown in FIGS. 1 and 2, a liner 30 is positioned in cavity 20. Liner30 includes a hot liner inlet 36 in communication with the hot inletport 24 and a cold liner inlet 38 in communication with the cold inletport 34. Illustratively, liner 30 is cylindrical about a central axis 29extending through liner 30. It is within the scope of this disclosurethat liner 30 may comprise more than one piece, as shown in FIGS. 1 and2.

As shown in FIGS. 1 and 2, a valve member 40 moves along axis 29 inliner 30 from a position permitting flow of hot fluid through the hotliner inlet to a position inhibiting flow of the hot fluid into mixingvalve 10. Valve member 40 moves either in an axially upstream direction25 or an axially downstream direction 27. It is within the scope of thisdisclosure that the valve member may comprise more than one piece, asshown in FIG. 13.

In thermostatic mixing valves, such as that shown in FIGS. 1 and 2, athermostat assembly 42 cooperates with valve member 40 to move the valvemember in response to changes in the mixed fluid temperature. As shownin FIG. 2, thermostat assembly 42 is positioned in valve body 12 andincludes a thermostat 44 and an actuator or pushrod 46 coupled tothermostat 44. Thermostat 44 includes a thermostat body 48. A thermallyresponsive fluid 50 is held in a cavity 54 formed in thermostat body 48by a bellows 52 sealed to the body 48. As the mixed fluid flows aroundand contacts thermostat 44, the volume of thermally responsive fluid 50changes in response to changes in the mixed fluid temperature, movingbellows 52. As bellows 52 moves, bellows 52 moves actuator 46 relativeto body 48 along central axis 29. It is understood that other types ofthermostats, as are known in the art, may be used within the scope ofthis disclosure.

As shown in FIG. 2, a first spring 55 biases valve member 40 in adownstream direction 27 toward a second or downstream valve seat 74. Asecond or return spring 57 is operatively coupled to thermostat 44 andvalve member 40. Return spring 57 cooperates with bellows 52 to limittravel of valve member 40 so that, under normal operating conditions,valve member 40 does not travel far enough downstream to seat againstsecond seat 74. Upon failure of bellows 52, first spring 55 moves valvemember 40 upstream and seats valve member 40 against second seat 74,preventing or reducing the flow of hot fluid into the mixing chamber 23.

Referring now to FIGS. 3A-3D, a liner 130 and valve member 140 moveablein liner 130 are shown. Liner 130 is generally cylindrical and has abore 164 therethrough in which valve member 140 moves to open and closehot liner inlet 136 and inhibit flow of hot fluid into the mixing valve.Valve member 140 cooperates with liner 130 to inhibit hot fluid flowthrough hot liner inlet 136 when the mixed fluid temperature is toohigh. Valve member 140 also cooperates with liner 130 to inhibit flow ofhot fluid past valve member 140 when the thermostat fails. As depictedin FIGS. 3A-3D, valve member 140 moves in liner 130 between a firstposition shown in FIG. 3A wherein the flow of hot fluid is restricted byvalve member 140 covering hot liner inlet 136, and a second positionshown in FIG. 3D wherein valve member 140 engages second seat 174 torestrict at least a majority of the flow of hot fluid.

Liner 130 includes an upstream region 166 having a first seat 168.Illustratively, a floor 172 of liner 130 provides first seat 168.However, other configurations are possible within the scope of thisdisclosure. Hot liner inlet 136 is shown in FIGS. 3A-3D as a slot formedin the side of liner 130. Cold liner inlet 138 is a slot formed in theside of liner 130 downstream of hot liner inlet 136. As shown in FIGS.3A-3D, liner 130 includes second seat 174 downstream of first seat 168and downstream of hot and cold liner inlets 136, 138. Second seat 174 isillustratively an annular flange 175 extending radially inwardly towardcentral axis 29. Illustratively, a wall 178 extends upstream from flange175 toward valve member 140, providing a seating surface 180 againstwhich valve member seats upon failure of the thermostat.

Valve member 140 includes a generally cylindrical portion 182 having adownstream end 184 and an upstream end 176. Upstream end 176 engagesfirst seat 168 to close hot liner inlet 136. As valve member 140 movestoward engagement with first seat 168, cylindrical portion 182 covershot liner inlet 136, restricting flow of hot fluid into valve body.Valve member 140 further includes a disc 188 coupled to downstream end184 of cylindrical portion 182 with a connection member 190. Disc 186includes an engagement surface 192 facing downstream to engage seatingsurface 180 of second seat 174.

When the temperature of the mixed fluid increases, thermally responsivefluid 50 expands, moving valve member 140 in an upstream direction. Asvalve member 140 moves upstream, valve member 140 moves toward a firstposition shown in FIG. 3A in which hot liner inlet 136 is closed byengagement of upstream end 176 and first seat 168. As valve member 140moves upstream, it covers increasing portions of hot liner inlet 136until it closes the inlet 136. In the first position, valve member 140closes hot liner inlet 136 and permits flow of cold fluid through coldliner inlet 138. As the temperature of mixed fluid decreases, thermallyresponsive fluid 50 contracts, and first spring (not shown) biases valvemember 140 in downstream direction 27. Valve member 140 thus movesthrough a position such as that shown in FIG. 3B, to an intermediate orthird position, such as the position shown in FIG. 3C, opening hot linerinlet 136 to permit hot fluid to flow therethrough. As shown in FIG. 3B,as valve member 140 moves in upstream direction 25, the sides ofupstream end 176 of cylindrical portion 182 cover hot liner inlet 136prior to engagement with first seat 168.

To prevent lock-up of valve 10, a weep opening or port 194 may be formedin disc 186 as shown in FIGS. 3A-3D to permit a substantially restrictedflow of fluid therethrough when valve member 140 engages second seat174. In operation, if the source of relatively hotter fluid fails, andno hot fluid flows into valve body 12, thermostat assembly 42 may movean amount so that valve member 140 engages second seat 174. Without weepport 194 permitting restricted flow of fluid therethrough, upon returnof hot fluid flow, valve 10 would remain in the position shown in FIG.3D. By permitting restricted flow of fluid through weep port 194, thethermostat assembly 42 can respond to the return of hot fluid and canmove valve member 140 from the position shown in FIG. 3D.

It is within the scope of this disclosure to provide a weep opening suchas weep port 194 in a wide variety of valve configurations.

Referring now to FIG. 4, an alternative liner 230 is shown. Liner 230 isformed to include a cold liner inlet 238 downstream of second seat 274.In this arrangement, valve member 240 shown in FIG. 4 cooperates withliner 230, specifically first and second seats 268, 274 and sides ofliner 230 adjacent hot liner inlet 236 to restrict hot fluid flow pastvalve member 240. Flow of cold fluid through cold liner inlet 238 is notdirectly restricted by movement of valve member 240. Cold liner inlet238 allows cold fluid to be provided regardless of failure of thermostator hot fluid supply.

Referring now to FIGS. 5-8, a valve member 340 is shown including mixingfins to increase turbulence and encourage mixing of fluids. As shown inFIGS. 5-8, valve member 340 includes a plurality of mixing fins.Different shapes of mixing fins 311, 321, and 331 are shown associatedwith valve member 340 in FIGS. 6, 7, and 8 respectively. Each of fins311, 321, and 331 extends radially outwardly from disc 386. Fins 311 ofFIG. 6 have lower surfaces 313 that are generally perpendicular tocentral axis 29. Fins 321 of FIG. 7 have lower surfaces 323 that faceradially inwardly and in upstream direction 25, toward cylindricalportion 382 of valve member 340.

Fins 331 of FIG. 8 have lower surfaces 333 that face substantiallyupstream toward cylindrical portion 382 of valve member 340. Lowersurfaces 333 of fins 331 are on a slant so that, when viewed lookingtoward a front 335 of one of fins 331, an upstream edge of first side337 is oriented downstream of an upstream edge of an opposite secondside 339 to form the slant. It is thought that such a slant could causevalve member 340 to spin with sufficient flow of hot and/or cold fluidflowing past fins 331. Mixing fins 311, 321, 331 are illustrativelyformed integral with disc 386, and investment casting is onemanufacturing technique contemplated to form disc 386 and fins 311, 321,331.

Referring now to FIG. 9, liner 430 is configured to encourage earliermixing of hot and cold fluids in a mixing valve. Liner 430 includes hotand cold liner inlets 436, 438 upstream of second seat 474. Slots 496 inthe side of valve member 440 align with cold liner inlet 438 to permitflow of cold fluid past valve member 440. Cold liner inlet 438 of liner430 is positioned closer to hot liner inlet 436 than to second seat 474.Slots 496 in valve member 440 are positioned closer to upstream end 476than to either downstream end 484 of cylindrical portion 482 or disc486.

Referring now to FIG. 10, liner 530 is configured so that hot linerinlet 536 is a bore formed in floor 572 thereof. First seat 568 projectsas a wall up from floor 572 to border the bore. Cold liner inlet 538 ispositioned in liner 530 downstream of the second seat 574, and is shownas a plurality of holes provided in the sides of liner 530. Second seat574 is illustratively an annular flange extending radially inwardlytoward central axis 29. Seating surface 580 of second seat 574 isprovided on a surface of seat 574 that faces upstream.

Valve member 540 is a “poppet” style valve member. Valve member 540includes disc 586, a centering portion 502 extending from an upstreamend 576 of disc 586, and a connection member 590 extending fromengagement surface 592 of disc 586. Connection member 590 extends beyondsecond seat 574 to engage an actuator (not shown). During thermostatfailure, first spring 555 biases valve member 540 such that engagementsurface 592 of valve member 540 engages seating surface 580 of secondseat 574, and these two surfaces engage to restrict the flow of hotfluid. In normal operation, when the mixed fluid temperature increases,the thermostat assembly moves valve member 540 in upstream direction 25toward a first position in which upstream end 576 of disc 586 engagesfirst seat 568, closing hot liner inlet 536.

As shown in FIGS. 10 and 11, centering portion 502 of valve member 540is illustratively a frustum of a right rectangular pyramid; the upstreamend 504 of centering portion 502 has an area less than the area of thedownstream end 506 connected to disc 586. Illustratively, as shown inFIG. 11, both of the ends 504, 506 of centering portion 502 fit in hotliner inlet 536 so that upstream end 576 can engage first seat 568. Thesmaller upstream end 504 and the pyramidal shape of centering portion502 assist with centering disc 586 so that the hot liner inlet 536 canbe closed. Although shown as a pyramid, other shapes would also properlyorient disc 586 as disc 586 moves toward engagement with first seat 568.Such shapes may include, but are not limited to, conical shapes,frustoconical shapes, paraboloidal shapes, or the like.

As shown in FIG. 12, liner 630 is modified from liner 530 of FIG. 10 bymoving the second seat 674 downstream of the cold liner inlet 638. Uponfailure of the thermostat, this arrangement restricts flow of both hotand cold fluid. During normal operation, valve member 640 throttles theflow of hot fluid to control the temperature of the mixed fluid.

Referring now to FIG. 13, liner 730 is similar to liner 530 of FIG. 10.Liner 730 includes a cold liner inlet 738 downstream of second seat 774.Connection member 790 is coupled to an upper piston 781 that moves inliner 730 adjacent cold liner inlet 738. Instead of permittingunrestricted flow of cold fluid as with certain previously describedliners, upper piston 781 throttles the flow of cold fluid during itsmovement in liner 730.

Upper piston 781 is generally cylindrical in shape and has an upstreamend 783 and a downstream end 785. Upstream end 785 includes inlet ports787 to permit flow of hot fluid from the hot liner inlet 736 throughupper piston 781. A central opening 789 is formed in upstream end 783and receives connection member 790 therein. A flange 791 is coupled toconnection member 790 and provides an engagement surface 793 whichcontacts upstream end 783 so that upper piston 781 and valve member 740move together. Sides 795 of the generally cylindrical upper piston 781are formed to include cold inlet holes 797 so that when sides 795otherwise cover cold liner inlet 738, flow of cold fluid enters throughcold inlet holes 797.

Cold liner inlet 738 is illustratively somewhat oversized compared withother cold liner inlets previously disclosed herein. In axial length,cold liner inlet has a length L2 that approximates the axial length L1of upper piston 781. As such, when valve member 740 is seated againstfirst seat 768, cold fluid flows through cold inlet holes 797 andbetween downstream end 785 and the downstream end of liner 730. Whenvalve member 740 is seated against second seat 774, cold fluid flowsthrough cold inlet holes 797 and inlet ports 787 in upstream end 785 ofupper piston 781. Thus, valve member 740 permits flow of cold fluid fromcold liner inlet 738 regardless of the position Of upper piston 781.

Referring now to FIG. 14, liner 830 is configured so that hot linerinlet 836 is a bore formed in floor 872 thereof. A wall 831 projectsupstream from floor 872 to border the bore. Wall 831 includes aninterior edge 833 that is illustratively beveled. Upstream end 876 ofvalve member 840 is a disc-shaped structure 835 and includes a groove837 around the outside thereof to receive a first o-ring 839. Aconnection member 841 extends from the disc-shaped structure 835 to afrustoconical region 843, which is connected to a generally cylindricaldownstream region 845 of valve member 840. Downstream region 845 isformed to include a groove 847 to receive a second o-ring 849 therein.

In operation, as the thermostat moves valve member 840 to close hotliner inlet 836, frustoconical region 843 cooperates with beveledinterior edge 833 to center second o-ring 849 with hot liner inlet bore836 as second o-ring 849 approaches the bore. Second o-ring 849 seatsagainst the axially inwardly-facing walls that define hot liner inlet836 to restrict flow of hot fluid therethrough. Upon failure of thethermostat, a spring (not shown) biases valve member 840 in a downstreamdirection 27 to a position wherein disc-shaped structure 835 is in hotliner inlet bore 836, and first o-ring 839 seats against the axiallyinwardly-facing walls that define hot liner inlet 836 to restrict flowof hot fluid therethrough. Because first and second o-rings 839, 849seat against the inwardly facing wall of the bore, assembly issimplified as valve member 840 can be simply “dropped in” liner 830.

It should be understood that some of the valve members—as drawn in FIGS.3A-9—are not drawn in proportion relative to the liners, but rather thesides of the valve members are drawn spaced apart from the inner wallsof the liners to facilitate discussion. In practice, as would beappreciated by one of ordinary skill in the art, the diameter of thevalve members is only slightly less than the diameter of the boresthrough the liners so that the valve members can move in the liners andprovide the necessary degree of closure of the liner inlet(s). As wouldbe understood by one of ordinary skill in the art, it is within thescope of this disclosure to provide first and second seats in a linerthat is a separate component coupled to the valve body or as part of thevalve body that serves as a liner. Although various openings to theliners and the valve members disclosed herein are shown as slots orholes, it should be understood that other suitable shapes and sizes arewithin the scope of this disclosure. As used herein, the terms“upstream” and “downstream” are used in the sense relative to thedirection of the flow of hot fluid through the cavity of the valve bodyduring normal operation of the mixing valve. Although specific featuresmay be shown in association with particular structure disclosed incertain embodiments, it should be understood that some of these featurescan be included in other embodiments, and the inclusion of thesespecific features with only some of the embodiments should not beconsidered as limiting.

Although a mixing valve has been described in detail with reference tocertain preferred embodiments, variations and modifications exist withinthe scope and spirit of the invention as described and defined in thefollowing claims.

1-29. (canceled)
 30. A mixing valve comprising a valve body including ahot fluid inlet for receiving a flow of hot fluid, a cold fluid inletfor receiving a flow of cold fluid, a mixed fluid outlet, a cavitybetween the mixed fluid outlet and the inlets, a first seat in thecavity, and a second seat in the cavity, and a valve member movable inthe cavity between a first position permitting flow of at least one ofthe hot and cold fluids and a second position restricting a majority offlow of hot fluid through the valve member, the valve member including aplurality of spaced-apart mixing fins configured to encourage mixing bycreating turbulence in fluid flowing past the mixing fins.
 31. Themixing valve of claim 30, further comprising a thermostat assemblymovable in response to changes in the temperature of the mixed fluid,the valve member being operatively coupled to the thermostat assembly tomove in response to movement of the thermostat assembly.
 32. The mixingvalve of claim 31, wherein the thermostat assembly includes a thermostatincluding a nested bellows.
 33. The mixing valve of claim 30, furthercomprising a liner in the cavity having a hot liner inlet coupled to thehot fluid inlet and a cold liner inlet coupled to the cold fluid inlet,wherein the hot liner inlet is a bore formed in a floor of the liner.34. The mixing valve of claim 33, wherein the valve member includes adisc having an upstream-facing surface for engaging the first seat whenthe valve member is in the first position and an oppositedownstream-facing surface for engaging the second seat when the valvemember is in the second position.
 35. The mixing valve of claim 30,further comprising a liner in the cavity having a hot liner inletcoupled to the hot fluid inlet and a cold liner inlet coupled to thecold fluid inlet, wherein the hot liner inlet is a slot formed in a sideof the line.
 36. The mixing valve of claim 30, further comprising aliner in the cavity having a hot liner inlet coupled to the hot fluidinlet and a cold liner inlet coupled to the cold fluid inlet, whereinthe liner includes the first and second seats, and the second seat isbetween the first seat and the cold liner inlet.
 37. The mixing valve ofclaim 30, further comprising a liner in the cavity having a hot linerinlet coupled to the hot fluid inlet and a cold liner inlet coupled tothe cold fluid inlet, wherein the liner includes the first and secondseats, and the cold liner inlet is between the second seat and the firstseat.
 38. The mixing valve of claim 30, further comprising a thermostatcoupled to the valve member to move the valve member in response tochanges in temperature of the mixed fluid, wherein the valve memberengages the second seat to inhibit flow of hot fluid, and the mixingvalve is formed to include a weep port to permit restricted flow of hotfluid to the thermostat when the valve member engages the second seat.39. A mixing valve comprising a valve body including a cold fluid inlet,a hot fluid inlet, a mixed fluid outlet, a cavity wherein fluid from thecold and hot fluid inlets flow together, the cavity having an upstreamregion and a downstream region, the downstream region being between theupstream region and the mixed fluid outlet, a first seat disposed in theupstream region, and a second seat disposed in the downstream region; athermostat assembly responsive to the temperature of the mixed fluid,the assembly movable between an extended position when the thermostatsenses a relatively higher temperature and a retracted position when thethermostat senses a relatively lower temperature; and a valve member inthe valve body movable in response to movement of the thermostatassembly between a first position engaging the first seat when thethermostat senses a first mixed fluid temperature, and a second positionengaging the second seat, in the first position the valve memberblocking the hot fluid inlet, the valve member moving to the secondposition in response to failure of the thermostat, and the valve membermoving to a third position between the first and second seats when asecond mixed fluid temperature lower than the first mixed fluidtemperature is sensed by the thermostat, wherein the valve member blocksthe cold inlet.
 40. The mixing valve of claim 39, wherein the valvemember includes an upstream region and a downstream region, thedownstream region engaging the second seat when the valve is in thesecond position, the downstream region formed to include a weep openingto permit restricted flow of fluid past the second seat when the valvemember is in the second position.
 41. The mixing valve of claim 39,wherein the valve member moves along an axis and includes a body and aplurality of spaced apart fins coupled to the body and extendingradially outwardly from the axis, the fins each including a surfacenon-parallel to the axis.
 42. The mixing valve of claim 41, wherein thesurface is substantially perpendicular to the axis.
 43. The mixing valveof claim 41, wherein the surface further extends upstream along theaxis.
 44. The mixing valve of claim 41, wherein each fin includes aradially outwardly facing front, a first side extending from the frontto the body, and an opposite second side extending from the front to thebody, the first and second sides each having an axially upstream edge,the surface extending between the upstream edges of the first and secondsides, the upstream edge of the first side being axially upstreamrelative to the upstream edge of the second side so that the surface isslanted.
 45. The mixing valve of claim 39, wherein the valve memberincludes a cylindrical portion to engage the first seat and a disccoupled to the cylindrical portion to engage the second seat. 46-49.(canceled)
 50. A mixing valve comprising a valve body providing a firstfluid inlet, a second fluid inlet, a mixed fluid outlet, and a cavityhaving a longitudinal axis, the cavity defined by at least one internalwall, and the cavity being in communication with the inlets and theoutlet, a first valve seat extending from the at least one internalwall, a second valve seat extending from the at least one internal wall,and a piston in the cavity and movable along the axis, the pistonincluding a piston bore extending longitudinally therethrough and havinga first piston end, a second piston end, an engagement surface at thefirst piston end bordering the piston bore and engaging the first seatto block flow of the first fluid through the piston bore, a failureshutoff surface at the second piston end movable to engage the secondvalve seat, the first fluid entering the piston bore between the firstvalve seat and the engagement surface, the piston including a slottherein positioned axially closer to the engagement surface than to thefailure shutoff surface to facilitate mixing of the first and secondfluids.
 51. The mixing valve of claim 50, further comprising a linerincluding the first and second valve seats.
 52. The mixing valve ofclaim 50, wherein the piston includes a plurality of spaced apartsurfaces non-parallel to the axis and arranged to at least partiallyface the direction of flow of fluid through the piston bore to encourageturbulent flow through the piston.
 53. The mixing valve of claim 52,wherein the plurality of surfaces is perpendicular to the axis throughthe cavity.
 54. The mixing valve of claim 52, wherein at least a portionof at least one of the plurality of surfaces is sloped, having aradially extending component and an axially extending component.
 55. Apiston for use in a fluid mixing valve, the piston comprising: a mainbody region and a plurality of spaced apart fins extending from the mainbody region, at least a portion of the fins configured to lienon-parallel to the direction of flow of at least one fluid through thevalve.
 56. The piston of claim 55, wherein each fin includes a surfacegenerally perpendicular to the axis.
 57. The valve member of claim 55,wherein the only connection between each of the plurality of fins is themain body region.
 58. The valve member of claim 55, wherein an axisextends longitudinally through the piston, each of the plurality of finsincludes a surface non-parallel to the axis, a front region, a left sideand an opposite right side, each side extending between the front regionand the main body region, the surface extending between a bottom edge ofeach of the left and right sides, the bottom edge of one of the left andthe right sides being axially upstream of the bottom edge of the otherside.
 59. The valve member of claim 58, wherein each of the plurality offins includes a radially outwardly facing front surface, and the onlyconnection between each of the plurality of structures is the main bodyregion.